Islands in Deep Time: Lost and Found Winter 2022

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Thousands of rocky islands sit on continental shelves, where they rise above sea level as drowned monadnocks. More are scattered across the oceans, where volcanic processes prevail. Due to their smaller size and distance from the nearest mainland, islands represent fragile settings where the balance between natural colonization and extinction is easily perturbed by human interference. With a recognizable geological history tracing back 500 million years, island paleoshores represent one of the oldest ecosystems on the planet. Former shores often reveal fossils preserved in life position (i.e. barnacles and corals), as well as distinct events related to storms. This course examines the geomorphology and paleontology of former islands preserved in the rock record, but now exhumed as fixed windows in ecological time showing how islands are created, how they disappear, and how life managed to reach distant outposts. Lectures include details on Wisconsin’s Baraboo Archipelago and South Dakota’s Black Hills in Cambrian time, the Ordovician Munk Archipelago on Canada’s Hudson Bay, Devonian Mowanbini Archipelago of Western Australia, Jurassic Saint David’s Archipelago of Wales, Cretaceous ErĂ©ndira islands of Mexico’s Pacific coast, ending with Pliocene and Pleistocene examples of oceanic islands in Portuguese Madeira, Azores, and the Cape Verde Islands. Since 2000, UNESCO has sponsored a system of international Geoparks, many of which feature unusual island settings and draw attention to Geoheritage. Some paleoislands have already achieved conservation as Geoparks and others are potential candidates. Course readings will be assigned from the existing scientific literature.
The Class: Format: lecture
Limit: 15
Grading: pass/fail only
Requirements/Evaluation: final project or presentation
Prerequisites: none
Enrollment Preferences: priority to first-year students with a demonstrated prior interest in or experience visiting national and state parks
Unit Notes: Markes Johnson is Professor Emeritus in the Geosciences Department at Williams College and the author of several books on the geology of islands in Mexico's Gulf of California and elsewhere.
Materials/Lab Fee: none

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